Radiative sky cooling is a passive cooling method to obtain the sub-ambient cooling phenomenon by dissipating waste heat into the cold outer universe, relying on the transparent atmospheric window (i.e., 8–13 μm). In recent years, radiative sky cooling has drawn much attention from the fields of engineering to materials due to its potential for energy-saving and low-carbon applications. Generally, an emitter that has high solar reflectivity and emits selectively within the whole atmospheric window is the best candidate for sub-ambient radiative sky cooling that can achieve a low cooling temperature. Here, we proposed a novel selective emissivity spectrum for radiative sky cooling based on the finding that there exists a large transmittance drop within the atmospheric window and this drop will harm radiative sky cooling process, breaking the inherent cognition of the optimal spectrum of the emitter. A theoretical analysis was conducted to predict the radiative sky cooling performance of the emitter with the novel spectrum, and the performance comparison to traditional ideal selective emitter has been demonstrated in terms of sub-ambient cooling temperature and maximum cooling power. Moreover, the underlying reasons and effective application conditions were discussed in detail. In addition, the effect of the parasitic cooling loss process and content of O₃ on the cooling performance of our proposed spectrum was investigated as well. In summary, this study provides a new thinking for designing spectrally selective emitters for obtaining remarkable lower cooling temperatures.

辐射天空冷却是一种被动冷却方法，依靠透明的大气窗口（即 8-13 μm）将废热散发到寒冷的外部宇宙中，从而获得亚环境冷却现象。近年来，天空辐射冷却因其节能低碳应用的潜力而受到工程领域和材料领域的广泛关注。通常，具有高太阳反射率并在整个大气窗口内选择性发射的发射器是可以实现低冷却温度的亚环境辐射天空冷却的最佳候选者。在这里，我们基于大气窗口内存在较大的透射率下降并且这种下降会损害辐射天空冷却过程的发现，提出了一种用于辐射天空冷却的新型选择性发射率光谱，打破对发射器最优频谱的固有认知。进行了理论分析以预测具有新光谱的发射器的辐射天空冷却性能，并在亚环境冷却温度和最大冷却功率方面证明了与传统理想选择性发射器的性能比较。此外，详细讨论了根本原因和有效应用条件。此外，寄生冷却损失过程和 O 含量的影响 并且在低于环境的冷却温度和最大冷却功率方面已经证明了与传统理想选择性发射器的性能比较。此外，详细讨论了根本原因和有效应用条件。此外，寄生冷却损失过程和 O 含量的影响 并且在低于环境的冷却温度和最大冷却功率方面已经证明了与传统理想选择性发射器的性能比较。此外，详细讨论了根本原因和有效应用条件。此外，寄生冷却损失过程和 O 含量的影响₃关于我们提出的光谱的冷却性能也进行了研究。总之，这项研究为设计光谱选择性发射器以获得显着更低的冷却温度提供了一种新思路。